System And Method To Partially Vaporize A Process Stream By Mixing The Stream With A Heating Medium

ABSTRACT

A system and method to partially vaporize a process or feed water stream does so in a liquid pool zone of a vessel as the stream comes into contact with a heating medium that is less volatile than the process stream. To keep the pool hot, the heating medium can be recirculated through a heater of a pump-around loop or a heater can be placed in the liquid pool. As the process stream is partially vaporized, any solids present in the process stream together with the unvaporized process or feed water stream move into the heating medium. These solids and unvaporized liquids may be further removed from the heating medium in the pool or in the pump-around loop. The vaporized process stream can be further condensed. Any heat recovered can be used to pre-heat the process stream or in the pump-around loop&#39;s heater in case of mechanical vapor recovery.

BACKGROUND

This disclosure is in the field of vaporization and desalinationprocesses such as, but not limited to, those used in mono ethyleneglycol (“MEG”) reclamation applications, seawater desalinationapplications, total dissolved solids reduction applications, and generalprocess water treatment for reuse or disposal.

Current vaporization and desalination processes are complicated,expensive, and typically require extensive pretreatment. In some cases,the cost of pretreatment exceeds the cost of the actual vaporization ordesalination processes. U.S. Pat. No. 8,652,304 B2 (“Nazzer”) disclosesa method of extracting dissolved or undissolved solids from a mixture ofwater and a process liquid or stream. The mixture is introduced into amixing zone within or upstream of a separation vessel where it isfurther mixed with a recycle fluid extracted from a liquid pool zone ofthe separator vessel and pumped through a heat exchanger.

Vaporization occurs in this mixing zone (where more than 99% of thevolatile components of the feed stream are vaporized). The resultingstream is then transferred to the separator vessel in which the vapor isseparated, with the solid and liquid components falling into the liquidpool zone of the separator vessel. A portion of these solids and liquidsthat bond to these solids then passes through a stripping zone of theseparator vessel. Water residing within the stripping zone displaces theliquids bound to the solids and an aqueous waste stream with dissolvedor nondissolved solids results.

Because this method requires a mixing zone for vaporization outside ofthe liquid pool, the required equipment is difficult to design and proneto scaling and plugging. The method also does not allow for vaporizationwithin the liquid pool and requires the heating medium—i.e., the recyclefluid, lighter than the water in the stripping zone—to be recycled at arate of at least ten times that of the process feed rate. This highrecycle rate is required because the method must limit the temperaturedifference between the recycle fluid and the process stream in order toavoid thermal degradation effects. Additionally, the method does notallow for partial vaporization with a blowdown.

Last, the method requires a stripping zone for solids removal. Astripping zone is prone to corrosion because of unvaporized (solids)components from the process stream. The stripping zone also presentssafety concerns due to the risk of higher temperature oil contactingwater. To reduce the safety concern, the oil must be cooled before ittouches the water in the stripping zone, but cooling the oil increasesits viscosity and ineffective solids separation results. The strippingzone does not allow for partial vaporization because partialvaporization can bring an extensive amount of unvaporized process liquidinto the stripping zone.

SUMMARY

The present disclosure allows partial vaporization to occur, simplifiesthe system and method of vaporizing a process (or feed water) stream,and reduces the cost of doing so.

Vaporization in a mixing zone outside of the liquid pool does not occurin embodiments of the system and method, nor do the system and methodhave a stripping zone for solids removal. The system and method is notlimited to a light heating medium relative to the process stream. Anypre-mixing of the process stream and heating medium may be done at alevel below that required for partial vaporization of the process orfeed water stream. Pre-mixing may also be done to provide a relativelysmall amount of vaporization to enhance the pre-mixing and acceleratethe fluid when it enters the liquid pool.

Embodiments of the system and method may disperse the process or feedwater stream into a liquid pool containing a hot heating medium that isless volatile than, and immiscible with, the process or feed waterstream. To keep the pool hot, the heating medium can be recirculatedthrough a heater in a pump-around loop. Alternatively or additionally, aheater can be placed in the liquid pool.

As the process stream is partially vaporized, any dissolved orundissolved solids present in the process or feed water stream come outof the stream together with the unvaporized process or feed water streamand move into the heating medium. The solids and unvaporized processstream or feed water that move into the heating medium may be furtherremoved from the heating medium within the vessel or in a separatorlocated in the pump-around loop. If the removal of solids andunvaporized liquids occurs in the vessel, the vessel should includeinternals of a kind known in the art to the separate the unvaporizedportion of the process or feed water stream from the heating medium. Ifthe removal of the solids and unvaporized liquids occurs in a separatorin the pump-around loop, the separator can be a hydrocyclone,centrifuge, particulate filter, settling tank, or some other piece ofseparation device equivalent to these.

In some embodiments, the vaporized process or water stream can becondensed or compressed and condensed. Heat recovered during condensingcan be used to pre-heat the process stream prior to its introductioninto the liquid pool, or to heat the heating medium in the pump-aroundloop.

The system and method can be used in applications such as but notlimited to MEG reclamation; seawater desalination; steam generation;total dissolved solids (“TDS”) reduction for produced water, desalterwash water, fracking flowback water, and amine reclamation. Unlike priorart systems and methods, there is no pretreatment of the process or feedwater stream or low temperature differentials between the vaporizationtemperature of the stream and heating medium (e.g., limited to 10° C.above the vaporization temperature due to the risk of scaling in theheat exchanger in the pump-around loop).

The embodiments of this disclosure may simplify the system and method topartially vaporize a process stream; reduce the costs associated withprior art partial vaporization systems and processes; eliminate thedesign and operational challenges presented by mixing zones locatedoutside of the liquid pool zone of the vessel and stripping zones forsolids and unvaporized process stream or feed water removal; andeliminate the prior art's limitation of not being able to be used inpartial vaporization applications in which a portion of the unvaporizedprocess or feed water stream remains in liquid form. The disclosureeliminates the need for light heating mediums relative to the process orfeed water stream. The disclosure also does not require the lowtemperature differential between the stream and heating medium orrecycle rates of at least 10 times greater than that of the processfeed.

The disclosure also reduces, and potentially eliminates, pretreatmentfor the process or feed water stream while at the same time minimizingor eliminating scaling and fouling of equipment. Any pre-mixing of theprocess or feed water stream and the heating medium that occurs outsideof the liquid pool zone may be done at a level below that at which thestream partially vaporizes. Pre-mixing may also be done to provide arelatively small amount of vaporization to enhance the pre-mixing andaccelerate the fluid when it enters the liquid pool.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the above recited features can be understood in detail, a moreparticular description may be had by reference to embodiments, some ofwhich are illustrated in the appended drawings, wherein like referencenumerals denote like elements. It is to be noted, however, that theappended drawings illustrate various embodiments and are therefore notto be considered limiting of its scope, and may admit to other equallyeffective embodiments.

FIG. 1 is an embodiment of a system and method to partially vaporize aprocess or feed water stream. A process stream having dissolved orundissolved solids is routed to a heating medium pool of a vessel. Asthe process stream partially vaporizes, dissolved solids may reachsaturation and turn to undissolved solids. The unvaporized portion ofthe process stream, including both solids and unvaporized liquids, movesinto the heating medium. The vessel includes internals to allow theseparation of the unvaporized portion of the process stream from theheating medium and remove the unvaporized portion of the process streamout of the vessel. A pump-around loop recycles and heats the heatingmedium. If any pre-mixing of the process stream and heating mediumoccurs outside of the liquid pool (see FIG. 6), the pre-mixing may be ata level below that at which vaporization occurs. Pre-mixing may also bedone to provide a relatively small amount of vaporization to enhance thepre-mixing and accelerate the fluid when it enters the liquid pool.

FIG. 2 is an embodiment of the system and method. The pump-around loopincludes a separator for removing solids alone or in combination withunvaporized liquid components of the process stream. The separator canbe a hydrocyclone, centrifuge, particulate filter, settling tank, orsome other piece of separation device equivalent to these.

FIG. 3 is an embodiment of the system and method. The vaporized processstream is partially condensed.

FIG. 4 is an embodiment of the system and method. Heat recovered fromcondensing is used to pre-heat the process stream prior to it beingrouted to the heating medium pool of the vessel.

FIG. 5 is an embodiment of the system and method. The vaporized processstream is compressed and this pressurized process stream is condensed inthe pump-around loop to help heat the heating medium being recycled inthe loop.

FIG. 6 is an embodiment of the system and method. Pre-mixing of theprocess stream and heating medium occurs outside of the liquid pool zoneof the vessel but at a level below that needed for vaporization.Pre-mixing may also be done to provide a relatively small amount ofvaporization to enhance the pre-mixing and accelerate the fluid when itenters the liquid pool

ELEMENTS AND NUMBERING USED IN THE DRAWINGS AND DETAILED DESCRIPTION

-   -   10 System or method    -   15 Process (or feed water) stream    -   15A Process stream prior to preheating    -   15B Pre-heated process stream    -   17 Mixer within or outside of 20    -   20 Vessel    -   21 Liquid pool zone    -   23 Heating medium    -   24 Interior volume    -   25 Unvaporized (dissolved and undissolved solids and unvaporized        liquids) portion of 15    -   27 Vapor separation zone    -   29 Vaporized volatile components of 15    -   30 Vaporized process stream    -   35 Removed heating medium stream or mixture (heating medium 23        and portion of 25)    -   40 Pump-around loop    -   41 Heater    -   45 Heated recycle stream substantially unvaporized portion-free        or with a reduced unvaporized portion 25 (relative to removed        stream or mixture 35)    -   47 Separator or separator device (such as a hydrocyclone,        centrifuge, particulate filter, settling tank or their        equivalents)    -   50 Heating medium stream substantially unvaporized portion-free        or with a reduced unvaporized portion 25 (relative to removed        stream or mixture 35)    -   60 Condenser    -   65 Partially or totally condensed process stream    -   70 Compressor    -   75 Pressurized stream

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of some embodiments of the present disclosure. However,it will be understood by those of ordinary skill in the art that thesystem and/or methodology may be practiced without these details andthat numerous variations or modifications from the described embodimentsmay be possible.

In the specification and appended claims, the terms “connect”,“connection”, “connected”, “in connection with”, and “connecting” areused to mean “in direct connect with” or “in connection with via one ormore elements”; and the term “set” is used to mean “one element” or“more than one element”. Further, the terms “couple”, “coupling”,“coupled”, “coupled together”, and “coupled with” are used to mean“directly coupled together” or “coupled together via one or moreelements”. As used herein, the terms “up” and “down”, “upper” and“lower”, “upwardly” and “downwardly”, “upstream” and “downstream”,“above” and “below”, and other like terms indicated relative positionsabove or below a given point or element and are used in this descriptionto more clearly describe some embodiments of the disclosure.

Embodiments of a system and method to partially vaporize volatilecomponents of a process or feed water stream achieve partialvaporization of those components in the liquid pool zone of the vesselwhen the stream contacts a heating medium residing in the liquid poolzone. The vessel is arranged to directly receive the process or feedwater stream, thereby eliminating pre-treatment between it and theupstream process providing the stream. A pump-around loop heats aportion of the heating medium and recycles this heated portion back tothe vessel.

The heating medium—which is immiscible with the stream and can belighter or heavier than the stream—is maintained at an operatingtemperature required for the desired partial vaporization effects.Pre-mixing may also be done to provide a relatively small amount ofvaporization to enhance the pre-mixing and accelerate the fluid when itenters the liquid pool. The vessel can also make use of blowdown toremove solids formed during the vaporization of the process or feedwater stream. Blowdown, as used here, refers to the removal of theunvaporized process (or feed water) stream with concentrated levels ofdissolved or undissolved solids. A separate vessel located in thepump-around loop can be used for the separation of the blowdown.

The different arrangements of the system and method 10 as shown in FIGS.1 to 6 route a process or feed water stream 15 into a vessel 20 whoseinterior volume 24 is defined by a liquid pool zone 21 and a vaporseparation zone 27. A heating medium 23 resides within the liquid poolzone 21 and this heating medium 23 is used to partially vaporize thevolatile components 29 of the process stream 15. Mixing of the processstream 15 and heating medium 23 occurs naturally within the liquid poolzone 21 as the process stream 15 enters the zone 21.

The now vaporized portions 29 of the process stream 15 migrate to avapor separation zone 27 of the vessel 20 and are removed as a vaporizedprocess stream 30. The vaporized process stream 30 can be routed to acondenser 60, as shown in FIGS. 3 and 4, to produce a partiallycondensed process stream 65. Heat from the condenser 60 can be recoveredand used to raise the temperature of the process stream 15A so thatstream 15 flows into the liquid pool zone 21 as a pre-heated processstream 15B.

The vaporized process stream 30 can also be routed to a compressor 70,as shown in FIG. 5. The now pressurized process stream 75 is condensedin the pump-around loop 40, with heat being recovered and used to heatthe recycle stream 45.

As the volatile components 29 of the process stream 15 vaporize, theunvaporized portion 25 of the process stream 15 moves into the liquidpool zone 21 along with the heating medium 23. Because the unvaporizedportion 25 is immiscible with the heating medium 23, that portion canseparate from the heating medium 23 in the vessel 20 or within aseparator 47 located in the pump-around loop 40. The unvaporized portion25, both liquid and undissolved solids, can be removed as blowdownstream 25. No stripping zone is used.

The separator 47 used in the pump-around loop 40 can be any separatorsuitable, including but not limited to a hydrocyclone, centrifuge,particulate filter, settling tank, or some other piece of separationdevice equivalent to these. A heating medium stream 50 with reducedamounts of, or without, unvaporized solids and liquids 25 exits theseparator 47 and passes through the heater 41. The heated recycle stream45 then recycles back to the liquid pool zone 21 of the vessel 20. Theheated recycle stream 45 may include some portion of the unvaporizedsolids and liquids 25 of the process stream 15.

The heating medium 23 is maintained at an operating temperature thatprovides the desired vaporization effects. The heating medium 23 can beany heating medium depending on the make-up of process or feed waterstream 15 and application-specific requirements. For example, theheating medium 23 could be one that one that is lighter than or heavierthan the process stream 15. However, the heating medium 23 is immisciblewith the process stream 15 to form a heterogeneous mixture with theprocess stream 15. The heating medium 23 is also less volatile than thevolatile components 29 of the process stream 15.

To keep the heating medium 23 at the selected operating temperature, aheater (not shown) can be placed in the liquid pool zone 21.Alternatively or additionally, a removed stream 35 of the heating medium23, which may include solids and unvaporized liquids 25 residing withinthe liquid pool zone 21, can be removed from the vessel 20 and routed tothe pump-around loop 40 and its heater 41. A heated recycle stream 45,that may include dissolved and undissolved solids and unvaporizedliquids 25, then recycles back to the liquid pool zone 21.

An embodiment of a method to partially vaporize a process streamincludes:

-   -   routing the process (or feed water) stream 15 directly into the        liquid pool zone 21 of the vessel 20 where it becomes mixed with        a heating medium 23 that is less volatile than the process        stream 15 and maintained at an operating temperature determined        by vaporization requirements to partially vaporize a volatile        components portion 29 of the process stream 15; and    -   removing the vaporized portion 29 of the process stream 15 from        the vapor separation zone 27 of the vessel 20 as a vaporized        process stream 30.

Prior to the process stream 15 entering the liquid pool zone 21 theremay be no pre-treatment of the stream 15 as it exits the upstreamprocess providing the stream 15 and there may be no mixing of theprocess stream 15 with the heating medium 23. Pretreatment meanstreatment such as but not limited to chemical dosing, filtration usingselectively permeable membranes, separators, or the use of ion exchange,deaerators or blowdown prior to the process stream 15 entering vessel 20(or some combination of the above pretreatment methods). (Coarsestraining of a kind known in the art and typically done ahead ofpretreatment might be used if the feed is taken directly from a naturalbody of water or from a source with excessive undissolved solids.) Ifany pre-mixing of the process stream 15 and heating medium 23 occursoutside of the liquid pool zone 21 (see e.g. mixer 17 in FIG. 6), thepre-mixing may be done at a level below that at which vaporizationoccurs. Therefore, partial vaporization of the process stream 15 occurswithin the liquid pool zone 21 of the vessel 20.

Pre-mixing may also be done to provide a relatively small amount ofvaporization to enhance the pre-mixing and accelerate the fluid 15, 45when it enters the liquid pool 21. The amount of vaporization thatoccurs in pre-mixing may be less than that which occurs in the liquidpool 21. For example, during normal (non-turndown) operations no morethan about 20% or about 5% of the volatile components in the stream 15may vaporize during pre-mixing. If the amount of vaporization doesexceed that of the liquid pool, during normal operations vaporizationduring pre-mixing should not exceed about 80% or about 90% of thevolatile components. Limiting the amount of vaporization duringpre-mixing helps avoid the design challenges and scaling and pluggingproblems associated with the mixing zone of the prior art (seeBackground).

The heating medium 23 and process stream 15 form a heterogeneous mixturewhen residing within the liquid pool zone 21. Additionally, the densityof the heating medium 23 can be greater than or less than that of theprocess stream 15.

The method can also include removing a portion 35 of the heating medium23 residing in the liquid pool zone 21 of the vessel 20; raising atemperature of the removed portion or stream 35 to produce a heatedrecycle stream 45; and routing the heated recycle stream 45 back to theliquid pool zone 21. The removed stream 35 can also be routed to aseparator 47 to produce heating medium stream 50 substantiallyunvaporized portion-free or with a reduced unvaporized portion 25. Oncestream 50 is heated by heater 41, it can be returned to the liquid poolzone 21 as the heated recycled stream 45 (also substantially unvaporizedportion-free or with a reduced unvaporized portion 25).

The method can also include condensing at least a portion of thevaporized process stream 30. Heat recovered from the condenser 60 can beused as pre-heating to raise the temperature of at least a portion ofthe process stream 15A prior to the process stream 15B entering theliquid pool zone 21 of the vessel 20. Alternatively or additionally, themethod can include compressing at least a portion of the vaporizedprocess steam 30. The pressurized stream 75 is then condensed in thepump-around loop 40 and used to raise the temperature of the recyclestream 45.

An embodiment of a system to partially vaporize a process streamincludes a vessel 20 arranged to contact a process or feed water stream15 exiting an upstream process and route the process stream 15 into aheating medium 23 residing within the liquid pool zone 21 of the vessel20. The interior volume 24 of the vessel 20 does not include a strippingzone for solids and liquids 25 removal. The heating medium 23 is lessvolatile than the process stream 15 and maintained at an operatingtemperature determined by vaporization requirements. The partiallyvaporized volatile components 29 of the process stream 15 migrate to thevapor separation zone 27 of the vessel 20.

A pump-around loop 40 is arranged to receive a portion 35 of the mixedheating medium 23 along with the non-volatile (dissolved andundissolved) components and unvaporized liquids 25 of the process stream15 that have moved into the heating medium 23 and then return theportion 35 back to the liquid pool zone 21 as a heated recycle stream45. The pump-around loop 40 of the system can also include a heater 41as well as a separator 47 arranged upstream of the heater 41 so that asubstantially unvaporized portion-free or reduced unvaporized portionheating medium stream 45 is being returned to the vessel 20.

Prior to contacting the heating medium 23, the process stream 15 may notbe mixed with the heating medium 23 outside of the liquid pool zone 21of the vessel 20. If any pre-mixing of the stream 15 and heating medium23 occurs, the mixing may be at a level below that required forvaporization of the volatile components 29. Pre-mixing may also be doneto provide a relatively small amount of vaporization to enhance thepre-mixing and accelerate the fluid when it enters the liquid pool 21.

The system can also include a condenser 60 arranged to receive at leasta portion of a vaporized process stream 30 exiting the vapor separationzone 27 of the vessel 20. Heat recovered from the condenser 60 can alsoserve as a pre-heater to raises the temperature of the process stream15A prior to the process stream 15B directly entering the liquid poolzone 21 of the vessel 20.

Alternatively or additionally, the system can include a compressor 70arranged to receive at least a portion of the vaporized process stream30. Heat recovered from condensing the pressurized stream 75 can be usedin the pump-around loop 40 to raise the temperature of the recyclestream 45.

Although the preceding description has been described herein withreference to particular means, materials, and embodiments, it is notintended to be limited to the particulars disclosed herein; rather, itextends to all functionally equivalent structures, methods, and uses,such as are within the scope of the appended claims.

What is claimed:
 1. A method to partially vaporize a process stream, themethod comprising: routing the process stream into a liquid pool zone ofa vessel, the liquid pool zone including a heating medium, the heatingmedium being less volatile than the process stream, immiscible with theprocess stream, and maintained at an operating temperature determined byvaporization requirements; partially vaporizing volatile components ofthe process stream due to contact with the heating medium in the liquidpool zone; and removing a vaporized portion of the process stream from avapor separation zone of the vessel as a vaporized process stream;wherein the interior volume of the vessel does not include a strippingzone for removal of an unvaporized portion of the process stream.
 2. Amethod according to claim 1 further comprising pre-mixing the processstream and the heating medium outside of the liquid pool zone of thevessel.
 3. A method according to claim 2 wherein during pre-mixing novaporization of the volatile components of the process stream occurs. 4.A method according to claim 2 wherein during pre-mixing no more thanabout 90% of the volatile components of the process stream vaporize. 5.A method according to claim 1 further comprising separating and removingat least some of the unvaporized portion from the vessel directly asblowdown.
 6. A method according to claim 1 further comprising: removinga portion of the heating medium residing in the liquid pool zone of thevessel; raising a temperature of the removed portion to produce a heatedrecycle stream; and routing the heated recycle stream back to the liquidpool zone.
 7. A method according to claim 6 wherein the removed portionof the heating medium is a mixture of heating medium and at least someof the unvaporized portion of the process stream.
 8. A method accordingto claim 7 further comprising separating and removing at least some ofthe unvaporized portion from the mixture prior to raising thetemperature.
 9. A method according to claim 1 further comprisingcondensing at least a portion of the vaporized process stream.
 10. Amethod according to claim 1 further comprising compressing at least aportion of the vaporized process steam.
 11. A method according to claim1 further comprising raising a temperature of at least a portion of theprocess stream prior to the process stream directly entering the liquidpool zone of the vessel.
 12. A method according to claim 1 wherein adensity of the heating medium is greater than that of the processstream.
 13. A method according to claim 1 wherein the process streamincludes water.
 14. A system to partially vaporize a process stream, thesystem comprising a vessel arranged to contact the process stream androute the process stream into a liquid pool zone of the vessel, theliquid pool zone including a heating medium less volatile than theprocess stream, immiscible with the process stream, and maintained at anoperating temperature determined by vaporization requirements; and apump-around loop arranged to receive a portion of the heating mediumresiding in the liquid pool zone and return the portion back to theliquid pool zone; wherein when the process stream is contacted by theheating medium in the liquid pool zone volatile components of theprocess stream partially vaporize and migrate to a vapor separation zoneof the vessel; wherein the vessel does not include a stripping zone forremoval of the unvaporized portion of the process stream.
 15. A systemaccording to claim 14 further comprising a mixer located outside of theliquid pool zone of the vessel and arranged to mix the process streamand the portion of the heating medium being returned to the vessel. 16.A system according to claim 15 wherein the mixer is arranged so novaporization of the volatile components of the process stream occurs inthe mixer.
 17. A system according to claim 15 wherein the mixer isarranged so no more than about 90% of the volatile components of theprocess stream vaporize in the mixer.
 18. A system according to claim 14wherein the vessel includes internals arranged to separate at least someof the unvaporized portion of the process stream from the heatingmedium.
 19. A system according to claim 14 further comprising thepump-around loop including a heater.
 20. A system according to claim 14further comprising the pump-around loop including a separation device.21. A system according to claim 14 further comprising a condenserarranged to receive at least a portion of a vaporized process streamexiting the vapor separation zone of the vessel.
 22. A system accordingto claim 14 further comprising a compressor arranged to receive at leasta portion of a vaporized process stream exiting the vapor separationzone of the vessel and produce a pressurized vaporized process stream.23. A system according to claim 14 further comprising a pre-heaterarranged to raise a temperature of the process stream prior to theprocess stream entering the liquid pool zone of the vessel.
 24. A systemaccording to claim 23 wherein the pre-heater is arranged to recover heatfrom a condenser arranged to receive at least a portion of the vaporizedprocess stream.